Mosaic tile calculator.

Use the initial geometry exercise: a 25 × 13-inch surface, one-inch square chips, twelve columns and twelve rows per sheet, no joints and a corner start. Each sheet face is twelve inches square. The surface needs three sheet positions across and two down: six source sheets.

Two sheets remain complete. Four lose rows, columns or both, yet every retained chip stays one inch square. The result is 325 whole chips and zero chip cuts. Those four trims are classified as backing-only. Four sheets per box gives two boxes, containing eight sheets: six sources and two carton extras.

Half an inch changes the cutting work

Increase only the width to 25½ inches. The source count stays at six, but the last chip column now contains thirteen half-width pieces. The inventory becomes 338 retained chips, including thirteen cuts. Choosing the lower whole-chip width restores 25 inches; the upper choice uses 26. Neither is an instruction to alter a finished wall.

Derive the face before adding a seam

A sheet with twelve chip columns contains eleven internal vertical joints. Its width is twelve chip widths plus eleven joints. Only after that face ends does the seam between sheets begin. Measuring loose mesh extending past the last chip as if it were tile face would enlarge the repeat incorrectly.

For a metric check, take two-by-two chips, each 10 mm square, with 2 mm internal joints. The sheet face is 22 × 22 mm. A 4 mm seam makes the repeat 26 mm. Across a 50 mm surface, two sheets end at 48 mm, leaving the final two millimetres in the gap region. The adjacent intact-chip endpoints are 48 and 62 mm.

What “backing only” actually establishes

The boundary misses every retained chip interior. That is a geometric fact about the entered grid, not a cutting instruction for paper, film or mesh. A tiny variation in the factory spacing can move a proposed line onto a chip. Inspect a physical sheet before preparing repeated strips.

MSI’s mosaic guide addresses inspection, alignment and cutting support. Its separate paper- and film-faced guide emphasizes sheet transitions and individual alignment. The mounting method and the product instructions determine how a mathematically valid trim can be made.

Keep leftovers attached to their source

The order deliberately does not exchange remnants between sheets. This makes every displayed chip traceable to a specific source. Reusing a strip can reduce purchases, but requires a separate check of its chip rows, dimensions, orientation and remaining mounting support. The unused-material figure counts chip faces left over, including untouched chips, rather than pretending the entire sheet rectangle was solid tile.

For individual larger tiles and angled patterns, use the individual tile cut planner. A pool band made from separate rectangular tiles has its own four-wall waterline layout; this sheet planner models one flat surface.

• Uniform rectangular chips in aligned rectangular sheets only. Irregular tesserae, interlocking boundaries and decorative arrangements cannot be represented by row and column counts.
• No openings, curves, slope, changes in thickness, grout depth or material suitability assessment.
• Sheet bounds can include a partial joint at the perimeter. Joint area is not a recommendation to fill movement clearances with grout.
• Nearest endpoint choices assume a top-left corner start and preserve your perimeter clearances. They do not optimize a centered arrangement.
• One source sheet per position; no offcut credit, saw kerf allowance or assumption that mesh can survive a particular trim.
• Up to thirty rows and columns per sheet, 2,500 source sheet positions and 100,000 retained chips. Split larger work into measured sections.